When a very small amount of substance can be quantitatively detected with high sensitivity in measurement for detection of biological substances such as protein and DNA, determination of the patient's condition and treatment can be promptly carried out. In view of this, an analysis method and an analysis device for quantitatively detecting weak light generated by a very small amount substance to be detected with high sensitivity are demanded. As an example of a method of detecting a substance to be detected with high sensitivity, a surface plasmon resonance fluorescence analysis method (Surface Plasmon-field enhanced Fluorescence Spectroscopy (SPFS)) is known.
The SPFS uses a prism having a metal film disposed on a predetermined surface. When the metal film is irradiated with excitation light through the prism at an angle which causes surface plasmon resonance, localized light (intensified electric field) can be generated on the surface of the metal film. With the localized light, a fluorescence material labelling the substance to be detected captured on the metal film is excited, and therefore the presence or the amount of the substance to be detected can be detected by detecting the fluorescence emitted from the fluorescence material.
In the SPFS, it is necessary to carry out positioning of the analysis chip with high accuracy in order to achieve detection with high sensitivity and high accuracy. While the incident angle of the excitation light is required to be adjusted with high accuracy to correctly detect the amount (density) of a substance to be detected, the incident angle of the excitation light cannot be adjusted with high accuracy when the position of the analysis chip is shifted. In addition, while it is preferable that the shape and the position of the irradiation spot of the excitation light and the shape and the position of the reaction site on the metal film coincide with each other to detect a substance to be detected with high sensitivity, the shape and the position of the irradiation spot of the excitation light cannot be adjusted with high accuracy when the position of the analysis chip is shifted when the position of the analysis chip is shifted. From the standpoint of usability, it is not preferable to require the user to carry out positioning of the analysis chip with high accuracy.
Some methods, which are not the SPFS, of positioning of an analysis chip have been proposed as the method of detecting a substance to be detected by irradiating an analysis chip with light. For example, PTL 1 discloses a technique in which two position confirmation holes are formed in an analysis chip (flow cell) in detection utilizing an SPR method. The user can adjust the position of the analysis chip with use of the position confirmation holes. In addition, PTL 2 discloses a technique in which an analysis chip (bio-chip) is irradiated with illuminating light having a wavelength different from that of excitation light to detect reflection light or transmission light of the illuminating light and specify the position of the analysis chip in detection utilizing a fluorescence material. With use of the illuminating light having a wavelength different from that of the excitation light, the position of the analysis chip can be specified while preventing discoloration of the fluorescence material.